Starring Jennifer Saunders and Timothy Spall, the series is set in 1929 and follows a chaotic family at the fictional Blandings Castle.
David Bamber and Harry Potter actor Mark Williams have also signed up to star in the show, which is based on PG Wodehouse's stories and will air as six self-contained episodes.
Spall plays Lord Emsworth (known as Clarence), who longs to be left at peace with his beloved pig The Empress, while Saunders stars as his sister Connie.
Williams will play Beach, Lord Emsworth's long-suffering and loyal butler. Bamber plays the role of Herr Schnellhund, Clarence's dance teacher.
Pramface star Jack Farthing has also been cast as Freddie, Lord Emsworth's unlucky-in-love and financially irresponsible son.
Walliams guest stars in two episodes as Rupert Baxter, Clarence's new secretary, and Faith plays dancer Georgia, who creates a stir when she accompanies Freddie to Blandings.
Tony Maudsley (Benidorm) plays Cyril Wellbeloved, who looks after The Empress, while Sam Hoare (Captain America: The First Avenger) plays 'Beefy' Bingham, who dreams of marrying Connie's daughter Gertrude.
Filming is currently underway on location at Crom Castle in Northern Ireland with the support of Northern Ireland Screen, and the series is due to air on BBC One and BBC One HD in the autumn.
The series is written and executive-produced by Guy Andrews.